1. Field of the Invention
The present invention relates to a digital broadcast/analog broadcast receiving and recording apparatus for receiving a digital broadcast signal and an analog broadcast signal, outputting a video signal and an audio signal of a selected channel, and recording digital data generated based on the digital broadcast signal and the analog broadcast signal.
2. Description of the Related Art
A digital broadcast/analog broadcast receiving and recording apparatus includes a circuit for receiving a digital broadcast signal and a circuit for receiving an analog broadcast signal and converts the received broadcast signal into digital data in a specific format such as an MPEG format, and records the digital data on a record medium such as a hard disk.
Upon reception of digital broadcast waves and analog broadcast waves, a tuner extracts and amplifies the digital broadcast signal or the analog broadcast signal of the selected channel. When the selected channel is of the digital broadcast signal, the digital broadcast signal is transmitted to a digital signal demodulation section, which then converts the digital broadcast signal into a transport stream (TSd) of digital data. When the selected channel is of the analog broadcast signal, an analog signal demodulation section demodulates the analog broadcast signal into a video signal and an audio signal and transmits the signals to an encoder, which then converts the signals into a transport stream (TSa) of digital data. Each of the transport streams (TSd and Tsa) is input through a system controller to a decoder, converted by the decoder into a video signal and an audio signal, and output from the decoder. The output video signal and audio signal are input to an analog television receiver for a viewer to view any desired program. When the viewer uses a remote controller to perform record operation, a CPU gives a record instruction to the system controller. The system controller stores received transport streams (TSd and Tsa) on a record medium separately.
As the C/N ratio of a digital broadcast signal falls below a predetermined threshold value, neither video nor audio is provided. Thus, when the reception state of a digital broadcast signal worsens, namely, the C/N ratio of the digital broadcast signal falls below the predetermined threshold value as an airplane passes through the face of an antenna, for example, while a digital broadcast receiving and recording apparatus (digital broadcast/analog broadcast receiving and recording apparatus) is receiving the digital broadcast signal, it is made impossible to view or record the video and audio during the worsened reception state. As the video and audio are thus interrupted, it is made impossible for the viewer to understand or follow the story of the program.
When recording a program, if digital broadcast signals are recorded from the beginning of the program, the portions of providing clear video before and after the broadcast is interrupted and the portion of no video are recorded. Thus, the viewer can later see only the program with the video interrupted and a problem as described above occurs. A Japanese unexamined patent publication JP-A-2001-285734 discloses a technique wherein when the digital broadcast is interrupted, a transition is made to the analog broadcast of the same program as interrupted to continue recording the program. However, when the digital broadcast is recovered from the interruption, recording the program in the analog broadcast is continued and thus when the viewer programs the apparatus to record a digital broadcast program by preference, the program in the analog broadcast is recorded and satisfactory video and audio cannot be provided for the viewer. As disclosed in a Japanese unexamined patent publication, JP-A-2001-320639, a technique is available wherein when the reception state of a digital broadcast worsens, the same program broadcast in a different time period is found and if the program exists, the same program in the different time is recorded. However, there is a sufficient probability that the program is not yet broadcasted at the point in time at which the viewer wants to play back the program; the program cannot reliably be recorded. If the program broadcast in the different time period is an analog broadcast, satisfactory video and audio cannot be provided against a viewer's will.
Since the viewer is to record the digital broadcast program because the digital broadcast provides better video and audio quality than the analog broadcast, it is desirable that the programs to be recorded should be those in digital broadcasts as much as possible.